Oral or nasal delivery of a medicament using an inhalation device is a particularly attractive method of drug administration as these devices are relatively easy for a patient to use discreetly and in public. As well as delivering medicament to treat local diseases of the airway and other respiratory problems, they have more recently also been used to deliver drugs to the bloodstream via the lungs, thereby avoiding the need for hypodermic injections.
It is common for dry powder formulations to be pre-packaged in individual doses, usually in the form of capsules or blisters which each contain a single dose of the powder which has been accurately and consistently measured. A blister is generally cold formed from a ductile foil laminate or a plastics material and includes a puncturable lid which is permanently heat-sealed around the periphery of the blister during manufacture and after the dose has been introduced into the blister. A foil blister is preferred over capsules as each dose is protected from the ingress of water and penetration of gases such as oxygen in addition to being shielded from light and UV radiation all of which can have a detrimental effect on the delivery characteristics of the inhaler if a dose becomes exposed to them. Therefore, a blister offers excellent environmental protection to each individual drug dose.
Inhalation devices that receive a blister pack comprising a number of blisters each of which contain a pre-metered and individually packaged dose of the drug to be delivered are known. Actuation of the device causes a mechanism to breach or rupture a blister, such as by puncturing it or peeling the lid off, so that when the patient inhales, air is drawn through the blister entraining the dose therein that is then carried out of the blister through the device and via the patient's airway down into the lungs. Pressurized air or gas or other propellants may also be used to carry the dose out of the blister. Alternatively, the mechanism that punctures or opens the blister may push or eject the dose out of the blister into a receptacle from which the dose may subsequently be inhaled.
It is advantageous for the inhaler to be capable of holding a number of doses to enable it to be used repeatedly over a period of time without the requirement to open and/or insert a blister into the device each time it is used. Therefore, many conventional devices include means for storing a number of blisters each containing an individual dose of medicament. When a dose is to be inhaled, an indexing mechanism moves a previously emptied blister away from the opening mechanism so that a fresh one is moved into a position ready to be opened for inhalation of its contents.
An inhaler of the type described above is known from the Applicant's own co-pending international application that has been published as WO2005/037353 A1.
According to one embodiment described and claimed in WO 2005/037353 A1, and illustrated in FIGS. 1 and 2 of the accompanying drawings, an inhaler 1 has a housing 2 containing a coiled strip of blisters 3. An indexing mechanism 4 comprising a single actuating lever 5 unwinds the coil 3 one blister at a time so that they pass over a blister locator chassis 6 and successively through a blister piercing station 7, when the actuator 5 is pivoted in a direction indicated by arrow “A” in FIG. 2. The blister 3a located at the blister piercing station 7 on each movement of the actuator 5 is pierced on the return stroke of the actuator 5 (in the direction indicated by arrow “B” in FIG. 2) by piercing elements 8 on the actuator 5 itself so that, when a user inhales through a mouthpiece 9, an airflow is generated within the blister 3a to entrain the dose contained therein and carry it out of the blister 3a via the mouthpiece 9 and into the user's airway.
The device known from WO2005/037353 A1 has already been modified so as provide a fully integrated device, i.e. one in which the used blisters are retained within its housing so that a user never has to come into direct contact with the blister strip. In one modified embodiment, known from the Applicant's own previous application that has now been published as WO09/007352 A1, there is provided a flexible and resilient spiral element mounted within the housing of the device into which the used portion of the blister strip is directed so that, as the strip is gradually used up, the spiral expands as more and more of the strip is fed or pushed into it between its coils. The inhaler of the present invention, in its preferred form, is also a fully integrated device that retains the used blisters, although in a preferred embodiment it has a wall to separate the interior of the housing into used and unused blister compartments. The wall is preferably rigid and slideably mounted so that the size of the unused and used blister compartments changes relative to each other as the number of blisters that are used increases and the number of unused blisters decreases.
The aforementioned document also describes an embodiment in which used blisters are crushed between the blister strip drive or indexing wheel and the inner surface of the casing of the device, which is also a feature of the inhaler of the present invention. As crushing takes place as the used strip passes around the blister strip drive member, a curl or curved form is imparted to the strip which helps it to coil up within the chamber.
The inhaler of the invention may also incorporate a blister strip drive mechanism or indexing mechanism that forms the subject of the Applicant's own previous international application that has now published as WO2009/092652 A1.
The disclosures of WO2005/037353 A1, WO09/007352 A1 and WO2009/092652 A1 are all incorporated herein by reference.